This invention relates to semiconductor devices and in particular to putting solder balls on semiconductor chips for connection onto a wafer.
As die sizes decrease with more components ( e.g., circuits, transistors, or the like) to provide more functions there are more connection points closer together. The distance between the connection points or the pitch becomes increasingly smaller as the die sizes decrease. Wire bonding of the connection points is used where these connection points are close together. It is highly desirable to provide solder bumps of larger and taller size to enable these chips to be directly connected to a substrate, package or circuit assembly without wire bonding. It is highly desirable to provide a solder ball on the die with as large a diameter and as high a height as possible without bridging the other solder balls to facilitate connections thereto. With a conventional circular resist defined, electroplated solder bump, the volume of plated solder and the resulting reflowed solder bump height is limited by the pitch of the product. The pitch is the distance from the center of one bump to the center of an adjacent bump.
In accordance with one embodiment of the present invention a variable cross-section plated mushroom with stud will allow the bumping of a larger diameter, taller bump on a tight pitch product.